RomanJoe wrote:

I mean a potential that need not be actualized for a thing to exist. For instance, the potential for certain atomic and subsequently subatomic particles to be structured in a specific way has to be actualized for a rubber sphere to be a rubber sphere. But the potential for it to be a red, yellow, green sphere or a sphere on the floor, on a shelf, in the air, are all irrelevant to its existence. Those potentials need not be actualized for it to be what it is. Even if it remained locked away in a cupboard and never actualized any of those potentials, it would still be a rubber sphere.

Well first there doesn't seem to be any difficulty here because these potentials don't self-actualise but are actualised by something else  if a rubber ball is red now then it is potentially green,then that potential could only be actualised by someone who could paint it green, secondly, you could say that being  red, yellow, green sphere or a sphere on the floor, on a shelf, in the air, etc is not essential to it but doesn't follow that its irrelevant to its existence because wherever a particular rubber ball exists it has some of those accidental properties i.e there could be no particular colourless rubber ball,ball not positioned somewhere etc...

RomanJoe wrote:

Good point, but would that make the First Way parasitic on the Existential Proof?

The First Way isn't parasitic on the existential proof. The former proceeds in terms of act and potency (in the broadest sense); the latter, in terms of the distinction between essence and existence. The person arguing the former doesn't need to turn to the essence-existence distinction to prove his thesis (see Neo-Scholastic Essays, pp. 89–90); by contrast, since the existential proof is centered around the essence-existence distinction, the person arguing the latter does need to turn to the essence-existence distinction.

Seriously, though, you should crack open some manuals for now and circle back to “the proofs” later.

John West wrote:

RomanJoe wrote:

Good point, but would that make the First Way parasitic on the Existential Proof?

The First Way isn't parasitic on the existential proof. The former proceeds in terms of act and potency (in the broadest sense); the latter, in terms of the distinction between essence and existence. The person arguing the former doesn't need to turn to the essence-existence distinction to prove his thesis (see Neo-Scholastic Essays, pp. 89–90); by contrast, since the existential proof is centered around the essence-existence distinction, the person arguing the latter does need to turn to the essence-existence distinction.

Seriously, though, you should crack open some manuals for now and circle back to “the proofs” later.

Ah, thanks for clarifying that. And, yes, I'm a novice to Thomism and I'm currently reading a few things to help me become more familiar with Thomism in general.

RomanJoe wrote:

Okay, let me revisit another point that I think is important. You brought up the principle that anything that is a composition of act and potency requires an actualizer outside of itself. I'm wondering whether or not it's possible for something to be purely actual with respects to its existence (not deriving its existence from any prior members) while being potential in other matters. These potentials may never be actualized, they may not have something outside of them to actualize them, but they're potentials and they're there. I would be fine seeing this as impossible if you could further justify the act/potency composition principle I referenced. 

No, because then that thing would not be really purely actual with respect to anything, in whatever manner it is operating is just one potential actualized among others it (it could have operated some other way) so such a thing would require actualization...as for the justification for the central causal principle I don't think I can do a better job if you have Feser's book.. I suggest you focus on background metaphysics more,as John has remarked ....specially give Ed's response to MacDonald a more careful read and again he do not himself acknowledge that first way do not prove pure actuality of first mover..